This invention relates to a sanitary napkin and, in particular, to one of a construction which incorporates a body fluid impervious layer that, for ease of manufacture, is laminated to a fibrous layer.
Sanitary napkins generally comprise a pad or core formed from one or more layers of hydrophilic material such as wood pulp, rayon, cotton, or some of the synthetic hydrophilic materials such as hydrophilic foams. The pad is generally rectangular in shape with one of its major surfaces designed to be worn against the body and the opposite major surface to be worn against the inner crotch portion of the user's undergarment. In order to protect such undergarment from stain and wetting, the garment facing surface and at least part of the longitudinal sides between major surfaces are covered by a body fluid impervious sheet. Such sheet generally comprises a thin film of a polyolefin with polyethylene being the material of choice in that polyethylene is highly suitable for this purpose, readily available and relatively inexpensive. The pad and its body fluid impervious sheet are generally overwrapped with an outer cover.
Recently, new products have been directed toward providing outer covers for such products which covers do not readily give a stained appearance after use. It has been discovered that such covers, comprised of hydrophobic materials such as hydrophobic fibrous fabrics or apertured films, will allow body fluid to pass readily into the absorbent pad but will not promote wicking of such fluid laterally along the surface of the cover and hence will limit the stained appearance of the cover to an essentially small fluid deposition area.
Unfortunately, it has been discovered that, in certain napkin constructions, the desirable attributes of non-staining are frustrated, notwithstanding the use of these newer cover materials. Specifically, certain napkin constructions have been employed wherein the body fluid impervious layer is laminated to a fibrous layer, e.g., tissue. This laminate structure has been employed primarily to facilitate the handling of the body fluid impervious material which generally has been in the form of a thin film which is slippery, flimsy, and subject to electrostatic charge and hence difficult to position properly about a pad during high speed manufacture. Further, the practice has been to manufacture such products by first wrapping a long snake or sliver of absorbent material with a continuous supply of impervious material and then subdividing or cutting such wrapped sliver into individual pads. Absent any processing aid, it has been essentially impossible to cut a wrapped sliver without displacing the impervious material.
Accordingly, one solution to this processing problem has been suggested in Canadian Patent Number 805,351 issued for "Napkin Construction" to Angelo P. Ruffo, et al. on Feb. 4, 1969. In accordance with the teachings of this Canadian patent, the impervious layer is laminated to a tissue layer which is substantially wider than the impervious layer and hence the longitudinal edges of the tissue layer extend beyond those of the impervious layer. This laminate is then wrapped about the pad so that the impervious layer extends to and covers the garment facing surface of the pad and a portion of the longitudinal sides of the pad. The wider tissue extends beyond the edges of the impervious layer and overlies the entire body facing surface of the pad. The tissue is of sufficient additional width so as to allow the longitudinal peripheral portions of the tissue layer to overlap on the body facing surface of the pad, securely holding the wrapper with its body impervious laminate in position for cutting and other handling.
A similar solution has been proposed in U.S. Pat. No. 3,230,955 wherein a fluid impervious sheet laminated to a tissue is employed as above with the exception that the tissue and impervious sheet are co-extensive and are held about the product by virtue of a "bridging" tissue ply which overlies the entire body facing surface of the product.
While both these methods are effective for facilitating the processing of napkins with impervious layers, they suffer from a common drawback which is particularly significant in view of recent efforts to produce a relatively stain free cover. Specifically, the extended portion of the cover overlying the body facing side of the napkin as disclosed in Canadian Patent 805,351 or the bridging ply, also overlying the body facing side of the napkin, as disclosed in U.S. Pat. No. 3,230,955 are both constructed of highly wicking material, e.g., tissue, primarily because of cost considerations. As such, when these materials are wetted with body fluid, they tend to wick such fluid laterally across the entire body facing surface of the napkin. As a result, notwithstanding the use of the recently developed non-wicking covers, the layer immediately below such cover becomes stained over a wide area, and this wide stain is visible through the cover and may even allow fluid to strike back through the cover, thus frustrating the purpose of these new covers. In view of the above problems, a need has arisen for a napkin construction which can facilitate the placement and stability of the impervious layer during manufacture but which will not frustrate the desirable clean and dry appearance of the napkin after use.